The eccrine sweat gland consists of an active secretory exocrine epithelium and duct which, depending on the species, may have a reabsorptive capacity. Although the isolation and investigation of the function of a single gland presents some technical difficulties, the use of an in vitro system seems to provide the most efficient approach to determine its mechanism of function in detail. Because of its simple tubular structure, the isolated sweat gland provides an excellent model for other exocrine glands (e.g., salivary glands, lacrimal glands and pancreas). In the proposed studies the interrelations of alpha and beta adrenergic and cholinergic stimulation will be determined in isolated human, monkey, rat and mouse sweat glands. Transmembrane and transepithelial electrical potential differences (p.d) will be measured in isolated monkey and rat eccrine sweat gland. The permeability of the secretory cell membrane to ions and the nature of the driving force for Na, Cl and K transport will be studied. The role of hydrogen transport as a regulating factor in sweat composition will be evaluated by studying the effect of acetazolamide, furosemide and HCO3 free medium on pH, sweat rate and the electrolyte content as well as permeability and p.d. of isolated monkey and rat sweat glands in vitro. With this in vitro system, we will also re-examine the possibility that the sweat duct dysfunction in cystic fibrosis is related to a defect in H ion-Na ion transport in the sweat duct.